In the field of semiconductor device manufacturing, microfabrication of a semiconductor substrate, such as a silicon wafer, is performed at times by plasma etching, which is one type of dry etching. During this etching process, a member inside a semiconductor device manufacturing apparatus that is exposed to reactive plasma may be subject to erosion (damage) and generate particles. Deposition of the generated particles on the semiconductor substrate may make it difficult to perform microfabrication as designed or cause contamination of the semiconductor substrate by elements contained in the particles. A thermal spray coating containing a rare earth element is therefore conventionally provided on a member exposed to reactive plasma during the etching process to protect the member from plasma erosion (see, for example, Patent Document 1).
However, even with a thermal spray coating containing a rare earth element, the generation of particles cannot be suppressed completely. In order to minimize the detrimental effects due to particles as much as possible, it is important first of all to reduce the number of particles deposited on the semiconductor substrate, and for this purpose, it is effective to reduce the size of particles generated when a thermal spray coating is subject to plasma erosion. This is because particles of small size are readily subject to erosion by the reactive plasma while being suspended in the etching process and eventually made to disappear by being gasified or are readily discharged to the exterior by being carried by a gas flow inside the semiconductor device manufacturing apparatus and are thereby prevented from depositing on the semiconductor substrate.
In addition to reducing the size of the particles generated, reduction of the contamination of the semiconductor substrate that is mainly caused by the element contained in the particles is also desired (see, for example, Patent Document 2). The degree of contamination can be evaluated by recovering and chemically analyzing a washing liquid that was used to wash the semiconductor substrate after the etching process. In the case where a member provided with a thermal spray coating containing a rare earth element as a main component is used in a semiconductor device manufacturing apparatus, particles generated from the thermal spray coating contains a large amount of the rare earth element. This may cause the rare earth element content in particles deposited on the semiconductor substrate to exceed an allowable level, which is called falling out of specifications.